Investments Investments (Equity Method Investments) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Schedule of Equity Method Investments [Line Items]
Share of results of affiliates, net	$ 33.4	$ (70.9)
VodafoneZiggo JV
Schedule of Equity Method Investments [Line Items]
Share of results of affiliates, net	61.1	(62.3)
Summarized results of operations of the VodafoneZiggo JV
Revenue	1,097.1	1,093.9
Loss before income taxes	124.9	(188.8)
Net loss	99.7	(150.3)
All3Media
Schedule of Equity Method Investments [Line Items]
Share of results of affiliates, net	(24.9)	(3.7)
Formula E Holdings Ltd (Formula E)
Schedule of Equity Method Investments [Line Items]
Share of results of affiliates, net	(1.2)	(0.4)
Other
Schedule of Equity Method Investments [Line Items]
Share of results of affiliates, net	$ (1.6)	$ (4.5)